do i need a durgo valve?

[alexg]

i'm having a new ensuite fitted in our loft room.

i've got the water supply issue sorted with a Techflow QT80-2-NHE negative head twin pump (thanks to the forum for providing the advice and resources for this particular aspect)

i now have to turn my attention to the subject of waste water.

as luck would have it, the waste stack (with exterior vent at the top) is almost immediately adjacent to the new bathroom location. the order of the waste will be sink (at the top of the flow), followed by bath and the wc).

would i be right in thinking that i have two options here.

1.) place a durgo valve upstream of the sink at the very head of the run to prevent any siphoning effects.

2.) feed each of the three applications directly to the existing waste stack via seperate waste pipes.

option 1. seems the simplest... but i'm no plumber, so am not even sure i need one fullstop.

cheers

 

[Richard C]

Make a separate stack connection for the W/C. You then have 2 options for the waste; fit separate waste runs for the bath & sink (preferred) or run the sink waste into the bath run & fit an anti-siphon trap to the sink or small air admittance valve between the bath & sink. Here’s a link to a useful guide that also incorporates Building Regs. requirements;

http://www.hunterplastics.co.uk/pdf/soilandwaste/swt_brochure.pdf

I assume you are aware what your doing must comply with BR’s & is notifyable work!

 

[alexg]

Make a separate stack connection for the W/C. You then have 2 options for the waste; fit separate waste runs for the bath & sink (preferred) or run the sink waste into the bath run & fit an anti-siphon trap to the sink or small air admittance valve between the bath & sink. Here’s a link to a useful guide that also incorporates Building Regs. requirements;

http://www.hunterplastics.co.uk/pdf/soilandwaste/swt_brochure.pdf

I assume you are aware what your doing must comply with BR’s & is notifyable work!

i've already notified BR and paid the fee...

my builder says that there is no way of connecting the wc to the stack independantly from the bath & wc, but adding aav or anti-siphon traps would be a possibilty... he's spoken to a plumber who doesn't seem to think there would be an issue fullstop, but i really can't see how i won't get a siphoning issue from the bath & sink upstream whenever the wc flushes?

 

[Richard C]

my builder says that there is no way of connecting the wc to the stack independantly from the bath & wc,

Why does he say that?

he's spoken to a plumber who doesn't seem to think there would be an issue fullstop,

Don't let him do the plumbing.

but i really can't see how i won't get a siphoning issue from the bath & sink upstream whenever the wc flushes?

Nor can I.

 

[alexg]

if i fit a AAV between the sink and the bath and then a second AAV between the bath and the join-up with the wc waste... will this cover all bases?

surely this would ensure that no siphoning occurs when either the bath or the wc is used?

or am i missing something?

cheers

 

[alexg]

I've been looking at all this again and it seems like the following is viable... please correct me if i am wrong.

the wc and bath/sink wastes will have to join before they reach the stack... it's not ideal, but there is no way round this (the stack is internal and short of removing a few ceilings, we will not be able to drop the bath/sink waste beneath the wc waste (which will already be at floor level) into the stack.

i will place a AAV upstream from the wc before the bath. i will then run the waste pipe upstream to the sink and have an anti-syphon trap on the sink... the waste run will end at this point.

(my only other option is placing the AAV between the bath and the sink which will mean a 32mm AAV rather than a 50mm AAV)

this seems right to me and should be relatively belt-and-braces.

anyone care to comment?

cheers

 

[Richard C]

If it’s an externally vented stack, why does the w/c entry have to be at floor level? Can’t you come off the w/c at 90 degrees into the stack with either a combined bath/basin waste running underneath into a boss fitting or even separate runs into a waste manifold? When the run is across the joists, the most common way of doing it is to locate the waste runs underneath the ceiling below & box in the pipes but if the run is with the joists, it usually possible to get enough fall within the depth of the joist; if not your probably exceeding the maximum branch length anyway.

Ultimately anything you do will have to meet the BR’s & the scrutiny of the Building Inspector who will come & look at & either pass or reject your installation; a 110mm w/c outlet must be ventilated with a 110mm AAV as far as I know! It’ difficult to visualise why you don’t appear to have enough space, could you post some pictures or a meaningful sketch might help.

 

[alexg]

Here is a basic sketch of the proposed order in the waste system.

waste stack

• alexg
• 30 Oct 2008
• 1

I'm not 100% sure why we cannot add a seperate waste entry to the stack for the bath & sink, but my builder tells me it isn't possible as the existing fitting (which I think is some kind of T/inspection end, which I guess was added in at the time of building the loft extension for this very purpose?) attaches to the top of the stack and sinks below the floor level... I suppose the issue is therefore accessing the joints etc?

Anyways... on the assumption that adding a second waste/stack connection is not viable, does the attached layout hold merit?

thanks

 

[Richard C]

I'm not 100% sure why we cannot add a seperate waste entry to the stack for the bath & sink, but my builder tells me it isn't possible as the existing fitting (which I think is some kind of T/inspection end, which I guess was added in at the time of building the loft extension for this very purpose?) attaches to the top of the stack and sinks below the floor level... I suppose the issue is therefore accessing the joints etc?

Sounds like a load of drivel to me; if the existing fittings aren’t suitable change them for ones that are. If you’re paying this builder to do the work for you he should be sorting out the drainage requirements in accordance with BR’s. I’ve never seen a sink/bath waste discharge directly into the side of a w/c outlet either in the flesh, the BR’s or in any of the design guides. I have some experience but I’m not a soil system expert & so am unsure if what you’re proposing will meet BR’s; a phone call to your LABC will confirm one way or the other.

Anyways... on the assumption that adding a second waste/stack connection is not viable, does the attached layout hold merit?

a 110mm w/c outlet must be ventilated with a 110mm AAV as far as I know!

You could extend the 110mm soil pipe beyond the w/c using a swept tee & create a vertical stub stack between the bath & w/c using another swept tee & then reducing down to 50mm for the bath waste I suppose but it’s going to look damn ugly!

No idea what your doing with the loft extension but if you’ve sub-divided to create the new bathroom using stud work, any wall between a room with a w/c & another habitable room (but not the room it serves in the case of an en-suite) must use “Sound Block” plasterboard & have a minimum 20mm of internal mineral sound insulation.

 

[Rico99]

Hi there,

You can have your bath/basin waste going into the toilet waste.

Their are specific pan connectors with bosses on for this.

Untitled

• Rico99
• 30 Oct 2008
• 1

Rico

 

[alexg]

I'm going to speak with Building Control this afternoon...

with regards to things looking ugly... all the piping will be hidden behind a false wall (the room is in the eves, so we will build false 1m high vertical walls to each side with the waste and supply pipes hidden behind).

as for having the bath & sink waste connecting up with the wc waste before heading into the stack... i appreciate that it is rare and not ideal, but until i can speak with Building Control this afternoon, it would be good to know whether it will or will not comply...

as for the stud walls... i think we are using sound board with that yellow wool insulation stuff inbetween... approx 100mm deep iirc.

 

[Richard C]

Interesting looking fitting posted by Rico not seen one of those before! May be OK for a washbasin but you couldn’t use it for the bath waste unless you either pump it or put the bath on a plinth! You’d still need to prevent siphoning the traps every time you flushed the loo though & then were back to the size of AAV required!

I'm going to speak with Building Control this afternoon...
as for having the bath & sink waste connecting up with the wc waste before heading into the stack... i appreciate that it is rare and not ideal, but until i can speak with Building Control this afternoon, it would be good to know whether it will or will not comply...

Probably best; for my own curiosity I would appreciate if you could post back what your LABC say.

 

[Rico99]

Richard C

Agree not ideal for a bath but they can be used horizontally as well, just wanted to show that this kind of fitting does exist.

Rico